1. Field of the Invention
The present invention relates to a low power, beam switchable, antenna arrangement and, more particularly, to a multibeam antenna arrangement wherein beam directional changes are accomplished by appropriately switching between each of a plurality of feeds which transmit low power signals and are disposed on a surface adjacent the focal surface of the antenna. The low signal power beam is intercepted by a separate antenna array disposed on the fourier transform surface of the surface on which the feeds are located, and the intercepted signal at each of the array elements is amplified to a proper high power level for transmission, and with an equal relative phase shift, before reradiating the beam to a destined receiver by a second antenna array.
2. Description of the Prior Art
Multibeam antennas are commonly constructed by placing different feedhorns or clusters of feedhorns at different locations in the focal plane of a parabolic reflector, each location corresponding to a different beam direction. Thus the beam direction can be switched by switching between the various feedhorns. In this regard see, for example, U.S. Pat. Nos. 3,914,768 and 4,236,161 issued to E. A. Ohm on Oct. 21, 1975 and Nov. 25, 1980, respectively.
In such arrangements, if the transmitting amplifier is placed before the switch, the switch must handle high power and be nearly lossless. If amplifiers are instead placed in each of the output ports of the switch, the unused amplifiers for any given switch position are wasting power.
The problem remaining in the prior art is to provide a multibeam antenna arrangement which permits beam scanning and overcomes the above-mentioned amplifier positioning problem and also allows for simplification of the beam forming elements without any penalty in efficiency and reliability.